That's why most states require landlords to install carbon monoxide detectors in each apartment they rent. (Ask your superintendent to install one if you live in an apartment and don't have one already).

Some states also require homeowners to have a CO detector, but even if your state doesn't, a carbon monoxide detector can save you or your family's life.

Carbon monoxide detectors often look like smoke detectors. For most people, a simple CO detector will suffice. They're battery-operated, wall-mountable devices that indicate something is wrong by beeping or chirping. Some carbon monoxide detectors use WiFi to connect with a smart home system. That might sound like overkill, but the expense can be worth it for caregivers who monitor a loved one from afar.

Here are the best-reviewed carbon monoxide detectors that have sold for $30 or less in the last 12 months:

Several Amazon customers called their gas company or fire department after this unit went off and discovered that a furnace or heater was leaking carbon monoxide. Some customers had difficulty mounting this unit to a wall, but most said it was easy to install.

Several Amazon customers say this CO detector saved their lives because it alerted them to a furnace or hot water heater that was leaking carbon monoxide. Some angry customers received an older unit that was nearing its expiration date, so be sure to check the unit’s born-on date (on any CO detector you buy).